If you are right between them, it really doesn't matter - you should be able to see the tower or know about where it is (within 5 miles of your place). Point the booster receiver to one of them. If it doesn't work, point toward the other one for a couple days. If you physically don't see or know where the tower is, drive around and look till you fine one. If you could get to tech support, they can tell you which tower serves you also - but the likely hood of that is like winner the lottery. Last time I had issure's, I got to 3 levels of customer service support management (Verizon)  and he told me which tower was to give me the service for my phone. And also suggested I move to a different carrier, which I did. Problem then solved